The mechanism of killer toxin is believed to relate to the inhibition of yeast cell wall ? glucan synthesis. Mannoprotein probably is one of the receptor for HM 1 killer toxin. The resistance is due to the decrease of N glycosylation of the sensitive yeast strain. HM 1 is a hydrophilic protein consisting of 88 amino acids. Two arginine residues located at positions 82 and 86 in the C terminal region of molecule are essential for the action of killer activity of HM 1 toxin. It is very useful to develop a novel anti fungal agent and prevent wild yeast contamination.